|Jmol-3D images||Image 1|
|Molar mass||393.35 g mol−1|
|Appearance||White crystalline solid|
220 °C, 493 K, 428 °F
decomposes at a higher temp.
|Solubility in water||<0.5 g/100 mL|
|Acidity (pKa)||~1.80 (20°C) |
|Flash point||Does not burn|
|Related compounds||EDTA, NTA|
| (what is: / ?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Pentetic acid or diethylene triamine pentaacetic acid (DTPA) is an aminopolycarboxylic acid consisting of a diethylenetriamine backbone with five carboxymethyl groups. The molecule can be viewed as an expanded version of EDTA and is used similarly. It is a white, water-soluble solid.
The conjugate base of DTPA has a high affinity for metal cations. Thus, the penta-anion DTPA5- is potentially an octadentate ligand assuming that each nitrogen centre and each COO–-group counts as a centre for coordination. The formation constants for its complexes are about 100 greater than those for EDTA. As a chelating agent, DTPA wraps around a metal ion by forming up to eight bonds. Transition metals, however, usually form less than eight coordination bonds. So, after forming a complex with a metal, DTPA still has the ability to bind to other reagents, as is shown by its derivative pendetide. For example, in its complex with copper(II), DTPA binds in a hexadentate manner utilizing the three amine centres and three of the five carboxylates.
Like the more common EDTA, DTPA is mainly used for sequestering metal ions that otherwise decompose hydrogen peroxide, which is used to bleach pulp in paper making. Several million kilograms are produced for this purpose annually.
Its chelating properties are useful in deactivating calcium and magnesium ions in hair products. DTPA is used in over 150 cosmetic products. Additionally, DTPA is used in MRI contrasting agents. DTPA improves MRI images by forming a complex with a gadolinium ion, which alters the properties of nearby water molecules.
DTPA has been considered for treatment of radioactive materials such as plutonium, americium, and other actinides. In theory, these complexes are more apt to be eliminated in urine. It is normally administered as the calcium or zinc salt, since these ions are readily displaced by more highly charged cations. DTPA forms complexes with thorium(IV), uranium(IV), neptunium(IV), and cerium(III/IV).
Compounds that are structurally related to DTPA are used in medicine, taking advantage of the high affinity of the triaminopentacarboxylate scaffold for metal ions.
- In ibritumomab tiuxetan, the chelator tiuxetan is a modified version of DTPA whose carbon backbone contains an isothiocyanatobenzyl and a methyl group.
- In capromab pendetide and satumomab pendetide, the chelator pendetide (GYK-DTPA) is a modified DTPA containing a peptide linker used to connect the chelate to an antibody.
- Pentetreotide is a modified DTPA attached to a peptide segment.
- DTPA and derivatives are used to chelate gadolinium to form a MRI contrast agent, such as Magnevist.
- Technetium is chelated with DTPA for ventilation perfusion scan (V/Q scan) and renal scan.
- Anonymous Pentetic Acid. In Dictionary of Organic Compounds, Sixth Edition; Buckingham, J., Macdonald, F., Eds.; CRC Press: 1996; Vol. 5, pp 1188.
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- Liu, Shuang (2008-09-15). "Bifunctional coupling agents for radiolabeling of biomolecules and target-specific delivery of metallic radionuclides". Advanced Drug Delivery Reviews 60 (12): 1347–70. doi:10.1016/j.addr.2008.04.006. ISSN 0169-409X. PMC 2539110. PMID 18538888.
- This article incorporates material from Facts about DTPA, a fact sheet produced by the United States Centers for Disease Control and Prevention.